Refrigerant expansion control



M. c. HARROLD ET AL REFRIGERANT EXPANSION CONTROL Nov. 6, 1956 Filed Dec. 4, 1953 Fig. 2

IN VEN TOR.

Marshall .6. Harm/d BY Harald A. Wheeler 1 3 The/r Attorney REFRIGERANT EXPANSION CONTROL Marshall C. Harrold and Harold A. -Wheeler, Dayton,

Ohio, assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application December 4, 1953, Serial No. 396,158 2 Claims. (Cl. 62-3) This invention relates to electrical apparatus and refrigerating apparatus and more particularly to electrically operated and controlled refrigerating systems which may be connected to power supply lines of such limited capacity in proportion to the size of the compressor motor of the refrigerating system that it is undesirable to cycle the compressor motor.

It is an object of my invention to provide a satisfactory control for controlling the refrigerating effect of a refrigerating system without cycling the compressor motor.

It is another object of my invention to provide a simple low cost refrigerant control for a refrigerating system in which the compressor motor is not cycled.

It is another object of my invention to provide a refrigerating system in which the refrigerant'flow between the condenser and the evaporator is controlled to provide two different rates of refrigerating effect.

it is another object of my invention to provide an improved flow control device for a refrigerating system.

It is another object of my invention to provide a simple low cost electrically operated valve arrangement.

These objects are attained in the form illustrated in the drawings by providing in the flow control restrictor between the condenser and the evaporator a bimetal operated valve heated directly by an electrical heating element under the control of a room thermostat switch for regulating the refrigerating effect applied to the room. in an alternative form the valve is operated by a closed bellows containing an electric heater and a volatile liquid.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the. accompanying drawings wherein a preferred form of the invention is clearly shown.

In the drawing:

Figure 1 is a diagrammatic view of a refrigerating system embodying my invention;

Figure 2 is an enlarged sectional view of the heat operated valve shown diagrammatically in Figure 1; and

Figure 3 is a sectional view of another form of heat operated valve such as is shown diagrammatically in Figure 1.

Referring now to the drawings and more particularly to Figure 1 there is shown an electrical power supply 29 which may have a limited capacity. Such a power supply is commonly found in residential districts. Connected by a manually operable switch 22 to the power supply 20 is a sealed electrical motor-compressor unit 24. This sealed motor-compressor unit may for example be provided with a split phase electric motor having a nominal rating up to 1 H. P. on a 115 volt power supply. The sealed unit 24 withdraws evaporated refrigerant from an evaporator 26 located in heat transfer relation with a room 23 or other enclosure to be cooled. The motor-compressor unit 24 compresses this evaporated refrigerant and forwards the refrigerant to a condenser 30 where the refrigerant is liquified. The liquid refrigerant flows from the condenser 30 through a capillary nited States Patent r: 2,769,312 1C6 Patented Nov. 6, 1956 restrictor flow control device 32 to the evaporator 26 where the liquid refrigerant evaporates under reduced pressure. An electric motor-driven fan 35 is provided for circulating air or other fluid from the room or enclosure 28 into a heat transfer relationship with the evaporator 26. This fan 35 is connected to the power supply 2%? and preferaly operates whenever the sealed motorcornpressor unit 24 operates.

The cycling of an electric motor upon a single phase residence power supply of volts is often objectionable and causes a light flickering. For this reason in some areas the electrical supply companies have prohibited the installation of cycling control arrangements for large motors in locations where such an installation will cause light flicker. With the increase in use of electr-ic motors in residential districts it is expected that such restrictions will become more and more wide spread. Yet a control of the refrigerating effect is very desirable and often very necessary.

According to my invention, I provide a valve 34 in series with the flow control device 32 which is controlled by the thermostatic switch 36 located in the room or enclosure 28. This valve 34 may be any suitable form of electrically operated valve but according to my invention I employ a simple heat operated valve which is actuated by the electric heater 38. This electric heater 33 is connected in series with the thermostatic switch 36 and the conductors 4th, 42 and 44 which are connected across the power supply 20.

Two different forms of electrically operated valves are shown in Figures 2 and 3. In Figure 2 there is shown a valve body 46 having its inlet and outlet connected in series with the capillary tube 32. The valve body 46 is provided with a valve seat 48. A disk valve 50 is provided for making sealing engagement with the valve seat 4-8 to stop the flow of refrigerant through the flow control device 32. The valve member 50 is connected to the end of a hairpin shaped bimetal member 52 having its lower portion anchored to the valve body at the point designated by the reference character 54. The bimetal 52 is arranged so that its low expanding face is outward. Within the looped-portion of the bimetal member 52 is an electric heater 38 which may be either of a ceramic type or a wire type. This heater 38 is connected by the conductors 42 and 44 through one or two sealed lead-in bushings 58 in the wall of the valve body 46 to the thermostat switch 36 and the power supply conductors 24).

With this arrangement when refrigeration is required in the room or enclosure 23, the switch 36 will move to the closed circuit position. This will close the circuit of the electric heater 38 and cause it to be heated and to heat the bimetal 52 to move the valve 59 to the open position shown in Figure 2. This will allow liquid refrigerant to iiow from the condenser through the capillary tube 32 to the evaporator where it will evaporate at reduced pressure and cool the air which is circulated in heat exchange relation with the evaporator before it is delivered to the room or enclosure 28. The heat from the heater 38 will keep the valve St} in the open position as long as the switch 36 remains closed. Should the temperature within the room or enclosure 28 fall below the point at which refrigeration is required the switch 36 will open to deenergize the heater 38. The refrigerant within the valve body 46 will rapidly cool the valve 50 and the bimetal 52 causing the bimetal 52 to move the valve 50 to the closed position in substantial sealing contact with its seat 48. The valve 50 will remain closed until the switch 36 recloses.

As an optional feature for systems of larger capacity a second capillary restrictor 60 may be provided between the condenser 30 and the evaporator 26 by-passing the valve 34 and the capillary restrictor 32. With this arrangernent when the valve 34 is opened the restrictors 32 and 60 operate in parallel to provide a relatively large flow of liquid refrigerant. When the valve 34 is closed by the opening of the switch 36 the flow of liquid refrigerant from the condenser 30 to the evaporator 26 is reduced to a predetermined amount. This will cause the evaporator to be pumped to a lower back pressure and because of the reduced liquid flow will reduce the refrig crating effect even though a portion of the evaporator 26 will be operated at a lower temperature. The remainder of the evaporator 26 will operate at a higher temperature and the average temperature of the evaporator 26 will be higher so that the refrigeration supplied in the room or enclosure 28 will be reduced.

Under this arrangement the only electrical load which is cycled is the relatively small load of the heater 38. This heater 38 may be as small as watt and this of course would not cause any light flicker or be objectionable in any way. With this arrangement therefore it is possible to make a relatively large installation in a residential district and still have automatic temperature control for the refrigerating system.

In Figure 3 there is shown a modified form of electrically operated thermal valve including a valve body 146 provided with a valve seat 148. A valve 150 preferably of natural or synthetic rubber is provided on the closed end of a metal or rubber or flexible plastic bellows 152. This bellows 152 is sealed by the sealing material 153 to the closed portion of the valve body 146. The bellows 152 contains a volatile liquid and an electric heater 138 of the wire or ceramic type. The terminals of the heater 13$ extend through sealing insulating bushings 158 in the valve body. The valve body 146 is provided with an inlet 172 and an outlet 174 which may be connected to the two portions of the capillary tube flow control device 32 as illustrated in Figures 1 and 2. In this form when the thermostat 36 is closed the heater 138 is energized to vaporize the volatile liquid within the bellows 152. The pressure applied by this volatile liquid is suflicient to expand the bellows 152 in the axial position until the valve 150 is moved into engagement with the seat 143. The deenergizing of the heater 138 will permit the volatile liquid within the bellows 152 to be cooled so that the pressure falls within the bellows 152. The volatile liquid in the bellows 152 may be some suitable refrigerant such as sulphur dioxide, ammonia or dichorotetrafluoro ethane or methyl or ethyl chloride. For use with Figure 3, the bimetal of the thermostat 36 must be reversed so that it closes when the temperature falls.

If desired the second capillary tube restrictor means 60 may be eliminated or permanently closed. This will cause the control to be entirely made by controlling the flow of refrigerant through a single restrictor 32.

In accordance with the provisions of Rule 78a, reference is made to the following prior filed application, S. N. 361,206, filed June 12, 1953, now patent No. 2,758,176.

While the form of embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted as may come within the scope of the claims which follow.

What is claimed is as follows:

1. In combination, a refrigerating apparatus including a closed refrigerating circuit having a motor compressor unit and a condenser and a flow control means and a single evaporator connected in circuit in the order named, said evaporator being located in heat exchange relation with a medium to be cooled, a manual control switch for continuously connecting said motor compressor unit to a power source for continuous operation, said flow control means including a restrictor and a valve means connected in series, said valve means having a heat motor for moving said valve means from one position to another, a control circuit including a heating means for said heat motor and a temperature responsive switch means located'in heat transfer relationship with and responsive to said medium to be cooled for controlling said system to regulate the temperature of said medium.

2. In combination, a refrigerating apparatus including a closed refrigerating circuit having a motor compressor unit and a condenser and a flow control means and a single evaporator connected in circuit in the order named, said evaporator being located in heat exchange relation with a medium to be cooled, a manual control switch for continuously connecting said motor compressor unit to a power source for continuous operation, said flow control means including a restrictor and a valve means connected in series, said .valve means having a heat motor for moving said valve means from one position to another, a control circuit including a heating means for said heat motor and .a temperature responsive switch means located in heat transfer relationship with and responsive to said medium to be cooled for controlling said system to regulate the temperature of said medium, said flow control means also, including a bypass containing a restrictor for bypassing said valve means.

References Cited in the file of this patent UNITED STATES PATENTS 1,969,102 Shenton Aug. 7, 1934 2,118,443 McCorkle May 24, 1938 2,128,020 Smilack Aug. 23, 1938 2,133,962 Shoemaker Oct. 25, 1938 2,169,554 Buchanan Aug. 15, 1939 2,675,683 McGrath Apr. 20, 1954 2,720,756 Stebbins Oct. 18, 1955 

